Inter-digitated capacitor in split-gate flash technology

ABSTRACT

The present disclosure, in some embodiments, relates to an integrated chip. The integrated chip includes a plurality of upper electrodes separated from a semiconductor substrate by a first dielectric layer. A lower electrode is laterally disposed between the plurality of upper electrodes and between sidewalls of the semiconductor substrate. A second dielectric layer lines opposing sidewalls and a lower surface of the lower electrode. The second dielectric layer laterally separates the lower electrode from the plurality of upper electrodes and from the sidewalls of the semiconductor substrate.

REFERENCE TO RELATED APPLICATIONS

This Application is a Continuation of U.S. application Ser. No.15/481,618, filed on Apr. 7, 2017, which is a Continuation of U.S.application Ser. No. 14/865,179, filed on Sep. 25, 2015 (now U.S. Pat.No. 9,691,780, issued on Jun. 27, 2017). The contents of theabove-referenced Patent Applications are hereby incorporated byreference in their entirety.

BACKGROUND

Flash memory is an electronic non-volatile computer storage medium thatcan be electrically erased and reprogrammed. It is used in a widevariety of electronic devices and equipment (e.g., consumer electronics,automotive, etc.). Common types of flash memory cells include stackedgate memory cells and split-gate memory cells. Split-gate memory cellshave several advantages over stacked gate memory cells, such as lowerpower consumption, higher injection efficiency, less susceptibility toshort channel effects, and over erase immunity.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates some embodiments of an integrated chip comprising adisclosed inter-digitated capacitor.

FIG. 2 illustrates some additional embodiments of an integrated chipcomprising a disclosed inter-digitated capacitor.

FIG. 3 illustrates some additional embodiments of an integrated chipcomprising a disclosed inter-digitated capacitor and a split-gate flashmemory cell.

FIG. 4 illustrates some alternative embodiments of an integrated chipcomprising a disclosed inter-digitated capacitor, a split-gate flashmemory cell, and a logic device.

FIGS. 5-16 illustrate some embodiments of cross-sectional views showinga method of forming an integrated chip comprising a disclosedinter-digitated capacitor.

FIG. 17 illustrates some embodiments of a method of forming anintegrated chip comprising a disclosed inter-digitated capacitor.

FIG. 18 illustrates some additional embodiments of a method of formingan integrated chip comprising a disclosed inter-digitated capacitor.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Embedded memory has become common in modern day integrated chips.Embedded memory is electronic memory that is located on a sameintegrated chip die as logic functions (e.g., a processor or ASIC). Onecommon type of embedded memory is embedded flash memory. Embedded flashmemory cells include a select gate arranged between first and secondsource/drain regions of a flash memory cell. The flash memory cell alsoincludes a control gate arranged alongside the select gate. The controlgate is separated from the select gate by a charge trapping dielectriclayer.

Data can be written to such a flash memory cell by applying voltages tothe select gate and to the control gate. Modern day flash memorytypically require high voltages (e.g., voltages greater than or equal toapproximately 14 V) to implement erase and program operations. Toachieve such high voltages, an integrated charge pump may be used.Integrated charge pumps use capacitors to store charge and then torelease the charge to achieve a high voltage. Typically, planarcapacitors, such as PIP (poly-interpoly-poly) capacitors, MIM(metal-insulator-metal), or MoM (metal-oxide-metal) capacitors are usedin integrated charge pump circuits. However, the formation of suchcapacitors uses extra masks and extra process steps that drive a highercost in flash technology.

In some embodiments, the present disclosure relates to aninter-digitated capacitor that can be formed along with split-gate flashmemory cells and that provides for a high capacitance per unit area, anda method of formation. In some embodiments, the inter-digitatedcapacitor comprises a well region disposed within an upper surface of asemiconductor substrate. A plurality of trenches vertically extend fromthe upper surface of the semiconductor substrate to positions within thewell region. Lower electrodes are arranged within the plurality oftrenches. The lower electrodes are separated from the well region by acharge trapping dielectric layer arranged along inner-surfaces of theplurality of trenches. A plurality of upper electrodes are arranged overthe semiconductor substrate at locations laterally separated from thelower electrodes by the charge trapping dielectric layer and verticallyseparated from the well region by a first dielectric layer.

FIG. 1 illustrates some embodiments of an integrated chip 100 comprisinga disclosed inter-digitated capacitor 101.

The integrated chip 100 comprises a well region 104 disposed within anupper surface 102 u of a semiconductor substrate 102. The well region104 has a higher doping concentration than the semiconductor substrate102. In some embodiments, the well region 104 may have a first dopingtype (e.g., n-type) while the semiconductor substrate 102 may have asecond doping type (e.g., p-type) different than the first doping type.A first dielectric layer 106 is arranged over the well region 104. Insome embodiments, the first dielectric layer 106 is in direct contactwith an upper surface of the well region 104.

A plurality of upper electrodes 112 are arranged over the semiconductorsubstrate 102. The plurality of upper electrodes 112 are verticallyseparated from the well region 104 by the first dielectric layer 106. Aplurality of lower electrodes 108 are laterally inter-leaved between theplurality of upper electrodes 112. The plurality of lower electrodes 108vertically extend from above the upper surface 102 u of thesemiconductor substrate 102 to within trenches extending into the wellregion 104, so that the plurality of lower electrodes 108 are embeddedwithin the well region 104.

A charge trapping dielectric layer 110 separates the plurality of lowerelectrodes 108 from the well region 104. The charge trapping dielectriclayer 110 vertically extends from within the well region 104 tolocations along sidewalls of the plurality of upper electrodes 112, sothat the charge trapping dielectric layer 110 laterally separates theplurality of lower electrodes 108 from the plurality of upper electrodes112. In some embodiments, the upper electrodes 112, the lower electrodes108, and the charge trapping dielectric layer 110 may have planar uppersurfaces that are vertically aligned (e.g., along line 114).

The plurality of lower electrodes 108 are electrically coupled togetherand the plurality of upper electrodes 112 are electrically coupled tothe well region 104, to form a potential difference between theplurality of lower electrodes 108 and the plurality of upper electrodes112 and the well region 104. Because the plurality of lower electrodes108 extend to locations embedded within the well region 104, theplurality of lower electrodes achieve a high-aspect ratio (e.g., a largeheight to width ratio) that allows the inter-digitated capacitor 101 toprovide for a high capacitance per unit area.

FIG. 2 illustrates some alternative embodiments of an integrated chip200 comprising a disclosed inter-digitated capacitor 201.

The integrated chip 200 comprises a well region 104 disposed within asemiconductor substrate 102. In some embodiments, one or more isolationstructures 202 may be arranged within the semiconductor substrate 102adjacent to the well region 104. The one or more isolation structures202 comprise a dielectric material, such as an oxide, for example. Insome embodiments, the one or more isolation structures 202 may compriseshallow trench isolation (STI) regions that protrude outward from anupper surface of the semiconductor substrate 102.

A first dielectric layer 106 is disposed onto a semiconductor substrate102 over the well region 104. In some embodiments, the first dielectriclayer 106 may comprise an oxide. A plurality of upper electrodes 112 aredisposed over the first dielectric layer 106. In some embodiments, theplurality of upper electrodes 112 may be in direct contact with an uppersurface of the first dielectric layer 106. A plurality of lowerelectrodes 108 are laterally arranged between the plurality of upperelectrodes 112. The plurality of lower electrodes 108 vertically extendfrom between the plurality of upper electrodes 112 to locations embeddedwithin the well region 104. In some embodiments, the plurality of lowerelectrodes 108 have rounded lower surfaces. In some embodiments, theplurality of upper electrodes 112 and the plurality of lower electrodes108 may comprise a conductive material, such as doped polysilicon or ametal (e.g., aluminum), for example.

The plurality of upper electrodes 112 comprise one or more innerelectrodes 112 b laterally arranged between outer electrodes, 112 a and112 c. In some embodiments, sidewall spacers 206 are arranged along afirst sidewall of the outer electrodes, 112 a and 112 c. A chargetrapping dielectric layer 204 is arranged along a second sidewall of theouter electrodes, 112 a and 112 c, and along opposing sidewalls of theone or more inner electrodes 112 b, so that the charge trappingdielectric layer 204 laterally separates the plurality of upperelectrodes 112 from the plurality of lower electrodes 108. The chargetrapping dielectric layer 204 is also arranged along sidewalls and lowersurfaces of the plurality of lower electrodes 108, so that the chargetrapping dielectric layer 204 separates the plurality of lowerelectrodes 108 from the well region 104. In some embodiments, theplurality of upper electrodes 112, the charge trapping dielectric layer204, the sidewall spacers 206, and the plurality of lower electrodes 108have planar upper surfaces that are vertically aligned.

In some embodiments, the charge trapping dielectric layer 204 maycomprise a tri-layer structure. In some embodiments, the tri-layerstructure may comprise an ONO structure having a first oxide layer 204a, a nitride layer 204 b contacting the first oxide layer 204 a, and asecond oxide layer 204 c contacting the nitride layer 204 b. In otherembodiments, the tri-layer structure may comprise anoxide-nano-crystal-oxide (ONCO) structure having a first oxide layer, aplurality of quantum dots contacting the first oxide layer, and a secondoxide layer contacting the first oxide layer and the plurality ofquantum dots.

A lower silicide layer 208 is arranged onto the well region 104 at alocation that laterally abuts the first dielectric layer 106. An uppersilicide layer 210 is arranged over the plurality of lower electrodes108 and over the plurality of upper electrodes 112. In some embodiments,the upper silicide layer 210 may comprise a plurality of segments thatare spaced apart according to the charge trapping dielectric layer 204.In some embodiments, the lower silicide layer 208 and the upper silicidelayer 210 comprise a nickel silicide.

In some embodiments, a contact etch stop layer 214 vertically extendsalong the sidewall spacers 206, and laterally extends over the lowersilicide layer 208 and the isolation structures 202. A first inter-leveldielectric (ILD) layer 216 is arranged over the contact etch stop layer214. The contact etch stop layer 214 laterally separates the first ILDlayer 216 from the sidewall spacers 206 and vertically separates thefirst ILD layer 216 from the lower silicide layer 208 and the isolationstructures 202. In some embodiments, a second dielectric layer 212 maybe arranged between the contact etch stop layer 214 and the isolationstructures 202. In some embodiments, the second dielectric layer 212 maybe a same material as the first dielectric layer 106.

The plurality of lower electrodes 108 are electrically connected to afirst voltage potential V₁, while the plurality of upper electrodes 112and the well region 104 are electrically connected to a second voltagepotential V₂. A difference between the first voltage potential V₁ andthe second voltage potential V₂ generates a potential difference betweenthe plurality of lower electrodes 108 and the plurality of upperelectrodes 112 and the well region 104. The potential differencegenerates an electric field that extends across the charge trappingdielectric layer 204. The electric field will cause charges having afirst sign (e.g., positive charges) to collect on the plurality of lowerelectrodes 108 and charges having an opposite, second sign (e.g.,negative charges) to collect on the plurality of upper electrodes 112and the well region 104. The potential of the charges stores energy inthe inter-digitated capacitor 201.

FIG. 3 illustrates some alternative embodiments of an integrated chip300 comprising a disclosed inter-digitated capacitor 201.

The integrated chip 300 comprises an embedded flash memory region 302 aseparated from a capacitor region 302 b by an isolation structure 202.The capacitor region 302 b comprises an inter-digitated capacitor 201having a plurality of lower electrodes 108 laterally inter-leavedbetween a plurality of upper electrodes 112. The plurality of lowerelectrodes 108 are separated from the plurality of upper electrodes 112and from a well region 104 by a charge trapping dielectric layer 204.Sidewall spacers 304 are disposed along outer sidewalls of the pluralityof upper electrodes 112 that are arranged between the plurality of lowerelectrodes 108 and the isolation structures 202. In some embodiments,the sidewall spacers 304 may comprise first sidewall spacers 304 a andsecond sidewall spacers 304 b. The first sidewall spacers 304 a and thesecond sidewall spacers 304 b may comprise a nitride (e.g., SiN), forexample.

The embedded flash memory region 302 a comprises one or more split-gateflash memory cells 306 a, 306 b laterally separated from theinter-digitated capacitor 201 by the isolation structure 202. In someembodiments, the embedded flash memory region 302 a comprises a pair ofsplit-gate flash memory cells having a first split-gate flash memorycell 306 a and a second split-gate flash memory cell 306 b. In someembodiments, the first split-gate flash memory cell 306 a and the secondsplit-gate flash memory cell 306 b are mirror images of one anotherabout an axis of symmetry.

The split-gate flash memory cells 306 a, 306 b respectively comprise acontrol gate electrode 312 and a select gate electrode 310 laterallyarranged between a plurality of source/drain regions 308 disposed withinthe semiconductor substrate 102. The plurality of source/drain regions308 vertically extending within the semiconductor substrate 102 to adepth d_(S/D) that is less than a depth d_(w) of the well region 104 inthe capacitor region 302 b. A gate dielectric layer 314 is arrangedvertically between the semiconductor substrate 102 and the control gateelectrode 312. The control gate electrode 312 is laterally separatedfrom the select gate electrode 310 by an additional charge trappingdielectric layer 204′ (e.g., an ONO layer) having an ‘L’ shapecomprising a lateral component and a vertical component. The lateralcomponent of the additional charge trapping dielectric layer 204′vertically separates the control gate electrode 312 from thesemiconductor substrate 102. In some embodiments, the lateral componentof the additional charge trapping dielectric layer 204′ may be separatedfrom the semiconductor substrate 102 by the gate dielectric layer 314.

Additional sidewall spacers 304′ are located along sidewalls of thecontrol gate electrode 312 opposing the select gate electrode 310. Theadditional sidewall spacers 304′ vertically extend from an upper surfaceof the control gate electrode 312 to the gate dielectric layer 314. Insome embodiments, the sidewall spacers 304 may comprise a first sidewallspacer 304 a and a second sidewall spacer 304 b.

A lower silicide layer 208 is arranged onto the source/drain regions308. The lower silicide layer 208 laterally abuts the gate dielectriclayer 314. An upper silicide layer 210 is arranged over the control gateelectrode 312 and the select gate electrode 310. In some embodiments,the contact etch stop layer 214 is laterally arranged over the lowersilicide layer 208 and along the additional sidewall spacers 304′, whilea first inter-level dielectric (ILD) layer 216 is arranged onto thecontact etch stop layer 214. In some embodiments, the first ILD layer216 may comprise a low-k dielectric layer, an ultra low-k dielectriclayer, an extreme low-k dielectric layer, and/or a silicon dioxidelayer. In some embodiments, the first ILD layer 216 has a planar uppersurface that underlies the upper silicide layer 210. In someembodiments, the planar upper surface of the first ILD layer 216 isvertically aligned with upper surfaces of the plurality of lowerelectrodes 108, the plurality of upper electrodes 112, the control gateelectrode 312 and the select gate electrode 310.

A second inter-layer dielectric (ILD) layer 316 is located over thefirst ILD layer 216. In some embodiments, the second ILD layer 316 maycomprise a low-k dielectric layer, an ultra low-k dielectric layer, anextreme low-k dielectric layer, and/or a silicon dioxide layer. Aplurality of contacts 318 comprising a conductive material extendvertically through the second ILD layer 316 to abut lower silicide layer208 and the upper silicide layer 610. In some embodiments, the pluralityof contacts 318 may comprise a metal such as tungsten, copper, and/oraluminum.

FIG. 4 illustrates some alternative embodiments of an integrated chip400 comprising a disclosed inter-digitated capacitor 201.

The integrated chip 400 comprises a capacitor region 302 b arrangedbetween an embedded flash memory region 302 a and a logic region 402.The capacitor region 302 b is separated from the embedded flash memoryregion 302 a and from the logic region 402 by one or more isolationstructures 202 arranged within a semiconductor substrate 102. Theembedded flash memory region 302 a comprises a plurality of split-gateflash memory cells 306 described above. The capacitor region 302 bcomprises an inter-digitated capacitor 201 described above.

The logic region 402 comprises a plurality of transistor devices 403 a,403 b. The plurality of transistor devices 403 a, 403 b respectivelycomprise a gate structure 407 laterally arranged between source/drainregions 404 located within the semiconductor substrate 102. Sidewallspacers 412 are arranged onto opposing sides of the gate structure 407.In some embodiments, the sidewall spacers 412 may comprise firstsidewall spacers 412 a and second sidewall spacers 412 b. In someembodiments, drain extensions regions 406 that are arranged within thesemiconductor substrate 102 may protrude outward from the source/drainregions 404 to under the sidewall spacers 412.

In some embodiments, the logic region 402 may comprise an NMOS region402 a having an NMOS transistor device 403 a and/or a PMOS region 402 bhaving a PMOS transistor device 403 b. In some embodiments, the NMOStransistor device 403 a comprises a high-k metal gate transistor havinga high-k gate dielectric layer 408 and an overlying NMOS metal gateelectrode 410 a. In some embodiments, the PMOS transistor device 403 bcomprises a high-k metal gate transistor having a high-k gate dielectriclayer 408 and an overlying PMOS metal gate electrode 410 b. The NMOSmetal gate electrode 410 a has a different work function than the PMOSmetal gate electrode 410 b. In some embodiments, the high-k gatedielectric layer 408 may comprise hafnium oxide (HfO), hafnium siliconoxide (HfSiO), hafnium aluminum oxide (HfAlO), or hafnium tantalum oxide(HMO), for example. In some embodiments (not shown), the high-kdielectric gate layer 408 may comprise a bottom high temperature oxidelayer and an overlying high-k dielectric layer.

FIGS. 5-16 illustrate some embodiments of cross-sectional views 500-1600showing a method of forming an integrated chip having an inter-digitatedcapacitor.

As shown in cross-sectional view 500 of FIG. 5, a semiconductorsubstrate 102 is provided. In various embodiments, the semiconductorsubstrate 102 may comprise any type of semiconductor body (e.g.,silicon/CMOS bulk, SiGe, SOI, etc.) such as a semiconductor wafer or oneor more die on a wafer, as well as any other type of semiconductorand/or epitaxial layers formed thereon and/or otherwise associatedtherewith.

A first dielectric layer 502 (e.g., SiO₂) is formed over thesemiconductor substrate 102. In some embodiments, the first dielectriclayer 502 comprises an oxide (e.g., SiO₂) formed by way of a thermalprocess or by a deposition process (e.g., chemical vapor deposition(CVD), physical vapor deposition (PVD), atomic layer deposition (ALD),etc.). A first masking layer 504 is formed over the first dielectriclayer 502. In some embodiments, the first masking layer 504 may comprisea silicon nitride layer. The semiconductor substrate 102 is selectivelyetched according to the first masking layer 504 to form isolationtrenches, which are subsequently filled with an insulating material toform one or more isolation structures 202 within the semiconductorsubstrate 102. The isolation structures 202 laterally separate anembedded flash memory region 302 a, a capacitor region 302 b, and alogic region 402.

As shown in cross-sectional view 600 of FIG. 6, a first implantationprocess is performed. The first implantation process selectivelyimplants a first dopant species 602 (e.g., boron, phosphorous, etc.)into the semiconductor substrate 102 according to a second masking layer604. In some embodiments, the second masking layer 604 may comprise thefirst dielectric layer 504. In other embodiments, the second maskinglayer 604 may comprise a photoresist layer. The first dopant species 602form a well region 606 within the semiconductor substrate 102. In someembodiments, after the first implantation process is finished, thedopant species 602 may be driven into the semiconductor substrate 102 byexposing the semiconductor substrate 102 to an elevated temperature.After the well region 606 is formed, the first dielectric layer 502 maybe removed.

As shown in cross-sectional view 700 of FIG. 7, a second dielectriclayer 701 (e.g., an oxide) is formed over the semiconductor substrate102. The first electrode layer 702 is formed over the second dielectriclayer 701 and a hard mask layer 704 is formed over the first electrodelayer 702. In some embodiments, the first electrode layer 702 maycomprise doped polysilicon. In some embodiments, the hard mask layer 704may comprise silicon nitride (SiN).

The first electrode layer 702 and the hard mask layer 704 aresubsequently patterned to define a plurality of select gate stacks 708and a plurality of upper electrode stacks 710. In some embodiments, thehard mask layer 704 may be patterned according to a photolithographyprocess. In such embodiments, the first electrode layer 702 isselectively exposed to an etchant in areas not masked by the hard masklayer 704 to form the plurality of select gate stacks 708 and theplurality of upper electrode stacks 710.

The plurality of select gate stacks 708 respectively comprise a selectgate electrode 310 and an overlying hard mask layer 704. The pluralityof upper electrode stacks 710 respectively comprise an upper electrode112 an overlying hard mask layer 704. After patterning, an oxide layer706 may be grown onto outer surfaces of the plurality of select gatestacks 708 and the plurality of upper electrode stacks 710. In someembodiments, the oxide layer 706 may be grown by way of a depositionprocess (e.g., CVD, PVD, ALD, etc.). The oxide layer 706 is configuredto protect the plurality of upper electrode stacks 710 during subsequentetching processes.

As shown in cross-sectional view 800 of FIG. 8, a third masking layer802 is formed over the semiconductor substrate 102. In some embodiments,the third masking layer 802 may comprise a photoresist layer. After thethird masking layer 802 is formed, a first etching process is performed.The first etching process exposes the well region 104 to a first etchant810 configured to etch the second dielectric layer 701 and the wellregion 104, to form a plurality of trenches 806 extending into the wellregion 104 between the upper electrodes 112.

As shown in cross-sectional view 900 of FIG. 9, a charge trappingdielectric layer 902 is formed. Within the embedded flash memory region302 a, the charge trapping dielectric layer 902 is formed on opposingsides of the select gate stacks 708. In some embodiments, the chargetrapping dielectric layer 902 within the embedded flash memory region302 a may have an ‘L’ shape with a lateral segment in direct contactwith the second dielectric layer 701. Within the capacitor region 302 b,the charge trapping dielectric layer 902 is formed on opposing sides ofthe plurality of upper electrode stacks 710. In some embodiments, thecharge trapping dielectric layer 902 may have an ‘L’ shape between anupper electrode stacks 710 and the isolation structures 202 and a ‘U’shape between adjacent upper electrode stacks 710. The charge trappingdielectric layer 902 lines the interior surfaces of the plurality oftrenches 806.

A second electrode layer 904 is formed onto lateral surfaces of thecharge trapping dielectric layer 902. Within the embedded flash memoryregion 302 a, the second electrode layer 904 forms control gateelectrodes 312. Within the capacitor region 302 b, the second electrodelayer 904 forms lower electrodes 108 extending into the plurality oftrenches 806. In some embodiments, the second electrode layer 904 maycomprise doped polysilicon or metal formed by a deposition process(e.g., CVD, PVD, ALD, etc.). A hard mask layer 906 may be formed overthe second electrode layer 904.

As shown in cross-sectional view 1000 of FIG. 10, a second etchingprocess is performed. The second etching process selectively exposes thecharge trapping dielectric layer 902, the second electrode layer 904,and hard mask layer 906 to a second etchant 1002. Within the embeddedflash memory region 302 a, the second etchant 1002 removes the chargetrapping dielectric layer 902, the second electrode layer 904, and thehard mask layer 906 between a first control gate stack 708 a and asecond control gate stack 708 b. Within the capacitor region 302 b, thesecond etchant 1002 removes the charge trapping dielectric layer 902,the second electrode layer 904, and hard mask layer 906 between theupper electrodes 112 and the isolation structures 202. In variousembodiments, the second etchant 1002 comprises a dry etch (e.g., aplasma etch with tetrafluoromethane (CF₄), sulfur hexafluoride (SF₆),nitrogen trifluoride (NF₃), etc.).

As shown in cross-sectional view 1100 of FIG. 11, a fourth maskingstructure 1102 is formed over the semiconductor substrate 102 in theembedded flash memory region 302 a and in the capacitor region 302 b. Insome embodiments, the fourth masking structure 1102 may comprise a BARC(bottom anti-reflective coating) formed over the semiconductor substrate102 through a spin-coating or other appropriate technique. In otherembodiments, the fourth masking structure 1102 may comprise aphotoresist layer.

After the fourth masking structure 1102 is formed, a third etchingprocess is performed. The third etching process selectively exposes thefirst electrode layer (702 of FIG. 10) and the hard mask layer (704 ofFIG. 10) to a third etchant 1104. The third etchant 1104 is configuredto selectively remove parts of the first electrode layer (702 of FIG.10) and the hard mask layer (704 of FIG. 10) within the logic region 402to define sacrificial gate stacks, 1106 a and 1106 b. The sacrificialgate stacks, 1106 a and 1106 b, respectively comprise a sacrificialpolysilicon layer 1108 and an overlying sacrificial hard mask layer1110. A first sidewall spacer layer 1112 may be formed along sidewallsof the sacrificial gate stacks, 1106 a and 1106 b. In some embodiments,the first sidewall spacer layer 1112 may comprise an oxide (e.g., SiO₂)or a nitride (e.g., SiN) formed by a deposition process.

As shown in cross-sectional view 1200 of FIG. 12, a second sidewallspacer layer 1202 may be formed along sidewalls of the select gatestacks 708 and the upper electrode stacks 710. A third sidewall spacerlayer 1204 may be subsequently formed along sidewalls of the select gatestacks 708, the upper electrode stacks 710, and the sacrificial gatestacks, 1106 a and 1106 b. In some embodiments, the second sidewallspacer layer 1202 and the third sidewall spacer layer 1204 may comprisean oxide (e.g., SiO₂) or a nitride (e.g., SiN) formed by a depositionprocess.

Source/drain regions, 308 and 404, are subsequently formed within theembedded flash memory region 302 a and within the logic region 402,respectively. The source/drain regions, 308 and 404, may be formed by asecond implantation process that selectively implants the semiconductorsubstrate 102 with a dopant species 1206, such as boron (B) orphosphorous (P), for example. The dopant species 1206 may besubsequently driven into the semiconductor substrate 102. The source anddrain regions, 308 and 404, extend into the semiconductor substrate 102to a depth that is less than a depth of the well region 104.

As shown in cross-sectional view 1300 of FIG. 13, a first salicidationprocess is performed to form a lower silicide layer 208 on uppersurfaces of the well region 104 and the source/drain regions, 308 and404. In some embodiments, the first salicidation process may beperformed by depositing a nickel layer and then performing a thermalannealing process (e.g., a rapid thermal anneal) to form a lowersilicide layer 208 comprising nickel.

A first planarization process is then performed along line 1302. Thefirst planarization process removes the hard mask layer and the chargetrapping layer from locations vertically overlying control gateelectrodes 312, the upper electrodes 112, and the sacrificialpolysilicon layer 1108. In some embodiments, the first planarizationprocess may comprise a chemical mechanical polishing (CMP) process.

As shown in cross-sectional view 1400 of FIG. 14, a contact etch stoplayer 1402 is formed over the semiconductor substrate 102, and a firstinter-level dielectric (ILD) layer 1404 is formed onto the contact etchstop layer 1402. In some embodiments, the contact etch stop layer 1402may comprise silicon nitride formed by way of a deposition process(e.g., CVD, PVD, etc.). In some embodiments, the first ILD layer 1404may comprise a low-k dielectric layer, formed by way of a depositionprocess (e.g., CVD, PVD, etc.).

As shown in cross-sectional view 1500 of FIG. 15, a second planarizationprocess is performed along line 1502. The second planarization processremoves parts of the contact etch stop layer 214 and the first ILD layer216 from locations vertically overlying control gate electrodes 312, theupper electrodes 112, and the sacrificial polysilicon layer (1108 ofFIG. 14). In some embodiments, the second planarization process maycomprise a chemical mechanical polishing (CMP) process, for example.

A replacement gate process is subsequently performed. The replacementgate process removes the sacrificial polysilicon layer and forms ahigh-k gate dielectric layer 408 at a position replacing the sacrificialpolysilicon layer using a deposition technique (e.g., chemical vapordeposition, physical vapor deposition, etc.). A metal gate electrode 410is deposited over the high-k gate dielectric layer 408 using adeposition technique. In some embodiments, an NMOS metal gate electrode410 a may be formed over the high-k gate dielectric layer 410 to form aNMOS transistor device within an NMOS region 402 a. In some embodiments,a PMOS metal gate electrode 410 b may be formed over the high-k gatedielectric layer 410 to form a PMOS transistor device within a PMOSregion 402 b. The NMOS metal gate electrode 410 a has a different workfunction than the PMOS metal gate electrode 410 b.

A second salicidation process is then performed to form an uppersilicide layer 210 on an upper surfaces of the control gate electrodes312, the select gate electrodes 310, the upper electrodes 112, and thelower electrodes 108. In some embodiments, the second salicidationprocess may be performed by depositing a nickel layer and thenperforming a thermal annealing process (e.g., a rapid thermal anneal) toform an upper silicide layer 210 comprising nickel.

As shown in cross-sectional view 1600 of FIG. 16, contacts 318 areformed within a second inter-layer dielectric (ILD) layer 316 overlyingthe first ILD layer 216. The contacts 318 may be formed by selectivelyetching the second ILD layer 316 to form openings, and by subsequentlydepositing a conductive material within the openings. In someembodiments, the conductive material may comprise tungsten (W) ortitanium nitride (TiN), for example.

FIG. 17 illustrates a flow diagram of some embodiments of a method 1700of forming an integrated chip having an integrated chip having aninter-digitated capacitor.

While the disclosed methods (e.g., methods 1700 and 1800) areillustrated and described herein as a series of acts or events, it willbe appreciated that the illustrated ordering of such acts or events arenot to be interpreted in a limiting sense. For example, some acts mayoccur in different orders and/or concurrently with other acts or eventsapart from those illustrated and/or described herein. In addition, notall illustrated acts may be required to implement one or more aspects orembodiments of the description herein. Further, one or more of the actsdepicted herein may be carried out in one or more separate acts and/orphases.

At 1702, a well region is formed within a semiconductor substrate.

At 1704, a plurality of upper electrodes are formed over the wellregion.

At 1706, the well region is selectively etched according to theplurality of upper electrodes to from one or more trenches laterallyseparating the plurality of upper electrodes.

At 1708, a charge-trapping dielectric layer is formed within the one ormore trenches and along sidewalls of the upper electrodes.

At 1710, lower electrodes are formed within the one or more trenches.The lower electrodes are separated from the well region and from theupper electrodes by the charge-trapping dielectric layer.

FIG. 18 illustrates a flow diagram of some additional embodiments of amethod 1800 of forming an integrated chip having an integrated chiphaving an inter-digitated capacitor. Although method 1800 is describedin relation to FIGS. 5-16, it will be appreciated that the method 1800is not limited to such structures, but instead may stand alone as amethod independent of the structures.

At 1802, isolation structures are formed within a semiconductorsubstrate to separate a capacitor region from an embedded flash memoryregion and a logic region. FIG. 5 illustrates some embodiments of across-sectional view 500 corresponding to act 1802.

At 1804, a well region is formed within the capacitor region. FIG. 6illustrates some embodiments of a cross-sectional view 600 correspondingto act 1804.

At 1806, a first electrode layer and a hard mask layer are formed overthe semiconductor substrate. FIG. 7 illustrates some embodiments of across-sectional view 700 corresponding to act 1806.

At 1808, the first electrode layer and the hard mask layer are patternedto define a plurality of upper electrode stacks within the embeddedflash memory region and select gate stacks within the embedded flashmemory region. The plurality of upper electrode stacks comprise upperelectrodes and an overlying hard mask layer. The plurality of selectgate stacks comprise a select gate electrode and an overlying hard masklayer. FIG. 7 illustrates some embodiments of a cross-sectional view 700corresponding to act 1808.

At 1810, the semiconductor substrate is selectively within capacitorregion to form one or more trenches. The one or more trenches arelaterally between the plurality of upper electrode stacks and verticallyextend to within the well region. FIG. 8 illustrates some embodiments ofa cross-sectional view 800 corresponding to act 1810.

At 1812, a charge trapping dielectric layer is formed within the one ormore trenches and along sidewall of select gate stacks and the upperelectrode stacks. FIG. 9 illustrates some embodiments of across-sectional view 900 corresponding to act 1812.

At 1814, control gates and lower electrodes are formed. The controlgates are formed at locations separated from the select gates and theupper electrodes are formed within the one or more trenches. FIGS. 9-10illustrate some embodiments of a cross-sectional view 900 correspondingto act 1814.

At 1816, the first electrode layer and the hard mask layer are patternedwithin the logic region to define sacrificial gate stacks. Thesacrificial gate stacks comprise a select gate electrode and anoverlying hard mask layer. FIG. 11 illustrates some embodiments of across-sectional view 1100 corresponding to act 1816.

At 1818, source/drain regions are formed within the embedded flashmemory region and the logic region. FIG. 12 illustrates some embodimentsof a cross-sectional view 1200 corresponding to act 1818.

At 1820, a lower silicidation layer is formed over the well region andover the source/drain regions. FIG. 13 illustrates some embodiments of across-sectional view 1300 corresponding to act 1820.

At 1822, a first planarization process is performed to remove the hardmask layer. FIG. 13 illustrates some embodiments of a cross-sectionalview 1300 corresponding to act 1822.

At 1824, a contact etch stop layer and a first inter-level dielectric(ILD) layer are formed over the semiconductor substrate. FIG. 14illustrates some embodiments of a cross-sectional view 1400corresponding to act 1822.

At 1826, a second planarization process is performed to remove parts ofcontact etch stop layer and first ILD layer. FIG. 15 illustrates someembodiments of a cross-sectional view 1500 corresponding to act 1826.

At 1828, an upper silicidation layer is formed over the lowerelectrodes, the select gates, and the control gates. FIG. 15 illustratessome embodiments of a cross-sectional view 1500 corresponding to act1828.

At 1830, contacts are formed within a second inter-level dielectric(ILD) layer formed over the first ILD layer. FIG. 16 illustrates someembodiments of a cross-sectional view 1500 corresponding to act 1830.

Therefore, the present disclosure relates to an integrated chip havingan inter-digitated capacitor that can be formed along with split-gateflash memory cells and that provides for a high capacitance per unitarea, and an associated method of formation.

In some embodiments, the present disclosure relates to an integratedchip. The integrated chip comprises a plurality of upper electrodesseparated from a substrate by a first dielectric layer. A plurality oflower electrodes vertically extend from between the plurality of upperelectrodes to locations embedded within the substrate. A charge trappingdielectric layer is arranged between the substrate and the plurality oflower electrodes and between the plurality of upper electrodes and theplurality of lower electrodes. The charge trapping dielectric layercomprises a plurality of discrete segments respectively lining opposingsidewalls and a lower surface of one of the plurality of lowerelectrodes.

In other embodiments, the present disclosure relates to aninter-digitated capacitor. The inter-digitated capacitor comprises aplurality of upper electrodes arranged over and separated from asubstrate by a first dielectric layer. A lower electrode is interleavedbetween the plurality of upper electrodes and is arranged withintrenches extending into the substrate. The lower electrode has asubstantially flat upper surface facing away from the substrate. Acharge trapping dielectric layer separates the lower electrode from thesubstrate and from the plurality of upper electrodes. The chargetrapping dielectric layer has outermost sidewalls arranged between theplurality of upper electrodes.

In yet other embodiments, the present disclosure relates to a method offorming an integrated chip. The method comprises forming a plurality ofupper electrodes over a substrate. The method further comprisesselectively etching the substrate according to a masking layer arrangedover the plurality of upper electrodes to form a trench that extendsinto the substrate and laterally separates the plurality of upperelectrodes. The method further comprises forming a charge trappingdielectric layer within the trench and along sidewalls of the pluralityof upper electrodes. The method further comprises forming a lowerelectrode on the charge trapping dielectric layer and within the trench.The lower electrode comprises a conductive material that continuouslyextends between opposing sidewalls of the trench and that is recessedbelow a top surface of the masking layer.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. An integrated chip, comprising: a plurality ofupper electrodes separated from a semiconductor substrate by a firstdielectric layer; a lower electrode laterally disposed between theplurality of upper electrodes and between sidewalls of the semiconductorsubstrate; a second dielectric layer lining opposing sidewalls and alower surface of the lower electrode, wherein the second dielectriclayer laterally separates the lower electrode from the plurality ofupper electrodes and from the sidewalls of the semiconductor substrate;and wherein the lower electrode has a bottommost surface that is abovethe semiconductor substrate and vertically below bottommost surfaces ofthe upper electrodes.
 2. The integrated chip of claim 1, wherein thelower electrode continuously extends between the opposing sidewalls ofthe lower electrode.
 3. The integrated chip of claim 1, wherein thesecond dielectric layer is a charge trapping dielectric layer.
 4. Theintegrated chip of claim 1, wherein the lower electrode has an uppersurface that continuously extends between sidewalls of the seconddielectric layer.
 5. The integrated chip of claim 1, further comprising:one or more sidewall spacers laterally separated from opposing sides ofthe lower electrode by the plurality of upper electrodes, wherein theone or more sidewall spacers have one or more upper surfaces that arearranged along a horizontal plane; and wherein the lower electrodevertically extends from directly between the sidewalls of thesemiconductor substrate to the horizontal plane.
 6. The integrated chipof claim 1, wherein the lower electrode is symmetric about a verticalline bisecting an upper surface of the lower electrode.
 7. Theintegrated chip of claim 1, wherein the plurality of upper electrodesand the lower electrode comprise polysilicon.
 8. The integrated chip ofclaim 1, wherein the second dielectric layer continuously extendsbetween the sidewalls of the semiconductor substrate.
 9. An integratedchip, comprising: a plurality of upper electrodes separated from asemiconductor substrate by a first dielectric layer; a lower electrodelaterally disposed between the plurality of upper electrodes and betweenfirst sidewalls of the semiconductor substrate; a second dielectriclayer separating the lower electrode from the plurality of upperelectrodes and from the first sidewalls of the semiconductor substrate,wherein the second dielectric layer continuously extends between thefirst sidewalls of the semiconductor substrate; and one or moreisolation structures laterally surrounding the plurality of upperelectrodes, wherein the one or more isolation structures comprise one ormore dielectric materials disposed directly between second sidewalls ofthe semiconductor substrate.
 10. The integrated chip of claim 9, whereinthe first dielectric layer has a substantially constant thicknessbetween the semiconductor substrate and the plurality of upperelectrodes.
 11. The integrated chip of claim 9, wherein a horizontalline extending along a bottom of the lower electrode extends through thesecond sidewalls of the semiconductor substrate.
 12. The integrated chipof claim 9, further comprising: a silicide layer disposed on thesemiconductor substrate laterally between outermost sidewalls of theplurality of upper electrodes and the one or more isolation structures.13. An integrated chip, comprising: a plurality of upper electrodesdisposed over a substrate; a lower electrode vertically extending frombetween the plurality of upper electrodes to within the substrate; asecond dielectric layer arranged between the substrate and the lowerelectrode and between the plurality of upper electrodes and the lowerelectrode; wherein the lower electrode has a rounded lower surfacefacing the substrate; and a silicide disposed over the lower electrodeand the plurality of upper electrodes, wherein the silicide hassidewalls that are laterally separated by a distance directly overlyinga top of the second dielectric layer.
 14. The integrated chip of claim13, further comprising: a first dielectric layer disposed between thesubstrate and the plurality of upper electrodes.
 15. The integrated chipof claim 14, further comprising: one or more sidewall spacers laterallyseparated from opposing sides of the lower electrode by the plurality ofupper electrodes, wherein the first dielectric layer extends fromdirectly below the plurality of upper electrodes to directly below theone or more sidewall spacers.
 16. The integrated chip of claim 13,wherein the second dielectric layer lines sidewalls and the roundedlower surface of the lower electrode.
 17. The integrated chip of claim13, further comprising: one or more isolation structures comprising adielectric disposed within the substrate and laterally separated fromthe second dielectric layer by the substrate; and an additional silicidedisposed on the substrate laterally between outermost sidewalls of theupper electrodes and the one or more isolation structures.
 18. Theintegrated chip of claim 1, wherein the lower electrode has a greaterheight at a lateral middle of the lower electrode than along outermostedges of the lower electrode.
 19. The integrated chip of claim 1,wherein the lower electrode is completely confined between the pluralityof upper electrodes.
 20. The integrated chip of claim 1, wherein thebottommost surface of the lower electrode continuously extends betweenopposing outermost sidewalls of the lower electrode.